Sphinx Modied Position For Scaphocephalic And Complex Craniofacial Patients. Technical Note

The development of less invasive surgical techniques means that surgical remodelling techniques can be performed at younger ages in more complex situations and at lower cost. We describe the technique of positioning and reviews our experience with the partially-modied sphinx position (MSP) in a serie of 234 patients, 96 of these endoscopic procedures (EP). Patient position on the operating table with regard to the treatment area, as well as the position of the treatment area in regard to the oor plane, is paramount for their anaesthetic and surgical management.


Background
The development of less invasive surgical techniques means that surgical remodelling techniques can be performed at younger ages in more complex situations and at lower cost.

Methods
Descriptive study

Results
We describe the technique of positioning and reviews our experience with the partially-modi ed sphinx position (MSP) in a serie of 234 patients, 96 of these endoscopic procedures (EP). Patient position on the operating table with regard to the treatment area, as well as the position of the treatment area in regard to the oor plane, is paramount for their anaesthetic and surgical management.

Conclusions
We consider that MSP is safe, facilitates access to the operative eld, shortens surgery time, reduces bleeding and offers maximum airway and cranio cervical safety in patients undergoing surgery to correct cranial vault pathologies.

Background
The development of less invasive surgical techniques means that cranial remodelling (CR) techniques can be performed at younger ages , ,complex situations, and at lower cost, posing a challenge for anaesthetists and surgeons.
Ideally, the patient's position should be stable enough to permit surgical manoeuvring and to reduce complications to the minimum, ensuring vascular and respiratory access and preventing accidental extubation.
The prone decubitus (PD) with cervical extension, also known as the sphinx position, is possibly the most complex and the one that has received the least attention, thus we review our experience with a MSP in a long series of patients.

Surgical Positioning And Procedures
Retrospective study of patients undergoing CR for scaphocephaly and other craneostenoses, operated in MSP. All patients placed in position always by expert paediatric neurosurgeon and anaesthesiologist.
The positioning process is described in Fig. 1. Brie y this position is achieved by rst placing the patient in prone decubitus, supporting the head on the malar region and leaving the ocular globes and orbits completely unobstructed. Two soft cotton and gauze rings, custom made for each patient, are used for support. Inclination may be varied depending on the area to be approached or type of procedure (video 1).
For EP, expanded suturectomy was the main surgical gesture, while for open approaches, modi cations of π procedure were preferred. In general complete suturectomy was avoided in open procedures in order to preserve sagital sinus area as possible, and sections of central bone around suture was prefered.
Resorbable plates were used to stabilize the bones keeping the galea separated from the dura for favoring cranial growth. Special care is taken to avoid manoeuvres which could exert pressure on the spine-cranium system or eyes supporting the head manually (Fig. 2).
Thomography images were taken in some cases during the operation and compared with pre-surgery images. All complications were analysed until patients were de nitively discharged (between 2-4 years after surgery).
Results 462 CR procedures performed over 16 years. 234 of which in MSP. 96 were EP. Patient ages from 7d to 24 months (mean 7 m).
No severe complications were observed during surgery and only one patient suffered a small lesion to the sagittal sinus, repaired without di culty. In 6 cases intra (MSP) and preoperative (SD) CT scans were compared; none showed hyperextension of the neck (Fig. 3) or compression of endotracheal tubes.
( Fig. 4) Initial position was not corrected in any patient and in only 18%, it was necessary to tilt the operating table to optimise access. In only one case, venous air embolism (VAE) were suspected, but it was not necessary to interrupt CR. No complications that could be attributed to the patient's position were observed until de nitive dismissal(2-4y).

Discussion
Early CR has been made possible thanks to the development of new surgical techniques and anaesthetic management but even considering that, patient's position on the operating table with regard to the treatment area, as well as in regard to the oor plane, and stabilization, is paramount for correct anaesthetic and surgical management preventing associated complications.
The use of head frames and classical stabilisation is not always possible in younger children a MSP, may involve complications and it is also completely impossible in newborns.
The two positions procedures, with SD for access to the anterior cranial vault and prone position (PP) for access to the posterior portion prevent cervical hypertension and jugular venous return is not compromised. However, simple PP fails to prevent increased intraocular pressure and lesions to the optical nerve and a second surgical procedure or re-positioning during surgery is required.
We have had very good results with a MSP. It that can be used in newborns and older children and does not require cranial stabilisation. Obviosuly, highly expert surgeons need to be involved to ensure that the head is always supported when there is a greater risk of pressure. (Fig. 2). In any case, and particularly in smaller children, it is normal practice for experienced paediatric neurosurgeons.
It consists of a PP with cervical extension -though not hyperextension -being thus suitable for patients with cervical abnormalities. Greater calvarial exposure is achieved by using a reverse Trendelenburg position with an inclination of 30-45° instead of hyperextension. In our series, no variation in the patient's position on the table was required during surgery, and we experienced no problems related with insu cient cranial access.
The head is supported on the malar region, resting on a padded surface customised to adapt perfectly to the size of each patient better that market solutions , , . avoiding changes in position and periodical head lifting.
MSP offers a balance between controlling the risk of venous haemorrhaging and VAE 4 . Except in one case, we have found no reports of serious complications when the head was supported in this position.
In MSP there is no over-extension of the cervical region, as we veri ed by CT scans (Fig. 4). Interestingly, we observed no changes in patients in the SD/MSP, possibly because posterior deformations in scaphocephalic children are associated with changes in the head-neck relationship. As far as we know, no studies objectively evaluating the cranial-spinal relationship in this type of surgery have been performed.
The tube placed between the two rings and combined with the non-hyperextended position helps to prevent accidental extubation without airway compromise. (Fig. 5).

Conclusions
MSP facilitates access to the operative eld, shortens surgery procedures, reduces bleeding from the dural sinuses and offers maximum airway safety in patients undergoing surgery to correct cranial vault pathologies. In our experience, it involves no substantial changes in the cranial-spinal relationship nor in the positioning of the airways and endotracheal tube.

Consent for publication
The videos and photos have been made with the aim of making the recognition of patients impossible. In any case, the parents or legal guardians have authorized the use of the images included in the article.

Availability of data and materials
The datasets and pictures used and/or analysed during the current study are available from the corresponding author on reasonable request. "Modi ed sphinx" position. This position is achieved by rst placing the patient in prone decubitus, supporting the head on the malar region and leaving the ocular globes and orbits completely unobstructed. Two soft cotton and gauze rings, custom made for each patient, are used for support. The endotracheal tube is guided between the two rings and easily connected to the ventilator and the tubing connecting the endotracheal tube to the respirator rests on the operating table. Cervical hyperextension is avoided by placing the body in the reverse Trendelenburg position with a 30-45° tilt. The degree of inclination may be varied depending on the area to be approached, ensuring no variation in cervical extension. The arms are placed forward to favour venous return.

Figure 2
The head is supported manually by the surgeon in the course of the operation. A: open procedure. B Endoscopic CR.